This invention relates to the process for producing xylyleneglycol by reacting xylylenediamine with nitrite.
Xylyleneglycol has the different characteristic from aliphatic glycol as the modifier or the raw materials of polyurethane or polyester resin and is recognized as an important material.
As the producing method of xylyleneglycol, the following methods are known so far.
(1) The process for producing xylyleneglycol by hydrolizing xylylene dichloride directly in the presence of alkaline compound or by converting xylylenedichlolide into diacetoxymethylbenzene and hydrolizing the resulting diacetoxymethylbenzene.
(2) The process for producing xylyleneglycol by reducing aromatic dicarboxylic acid ester by hydrogen in the presence of a catalyst.
The first method has the defects, such as it requires a pressure vessel, requires a long reaction time and the process is long and complicated. In addition, it also has the essential defects, that is, the xylylenedichloride which is the raw material of the first method is produced by chlorination of xylene in general, but in that case, each of the two methyl groups which substitute aromatic nucleus cannot be monochlorinated selectively. And as the result, not only multichlorination of the methyl groups or chlorination of aromatic nucleus occurs simultaneously, useless chlorides are by-produced and the yield of objective product is decreased, but also the separation and purification of the reaction product are not easy (Japanese Patent Publication No. 54491/1982).
The second method is disclosed in Japanese patent publication No. 22814/1972, which method requires a pressure vessel and as the conversion rate of the reaction should be suppressed to prevent side-reaction, objective xylyleneglycol is obtained as the mixture with raw material and intermediate product. This requires separation of xylyleneglycol from the reaction mixture and recycling of the raw material and intermediate product to the reaction system. This separation process is not so easy and one pass conversion is low, so that the second method is also not an advantageous method industrially.
The present inventors studied the process for producing xylyleneglycol by reacting xylylenediamine with nitrite in the presence of mineral acid to solve the defects in the prior arts and to establish an industrially advantageous method.
It is well known that diazonium compound is formed by reacting primary amines with nitrite in the acidic solution and the reaction is called diazotization reaction. It is also well known that diazonium compound obtained by diazotization reaction of aliphatic primary amine is instable and decomposes to alcohol or olefine by water. However, the method for producing alcohol derivative by diazotization reaction of benzylamine or its derivatives, of which general formula is shown as ##STR1## and decomposing the resulting diazonium compound is not known except a few examples for the producing method of alcohol having special substituents, such as the producing method of p-diethylaminomethyl benzylalcohol from p-diethylaminomethyl benzylamine (Methoden der Organischen Chemie). Therefore the method for producing xylyleneglycol from xylylene diamine is not disclosed. When benzylamine derivative, especially xylylenediamine is diazotized and the resulting diazonium compound is decomposed to produce alcohol derivative, tarry material is easily formed and the yield of the objective alcohol derivative is low. For example, when the diazotization reaction of xylylenediamine is carried out by adding 2.5 to 3.0 mols of hydrochloric acid based on 1 mol of amino group (5.0 to 6.0 mols of hydrochloric acid based on 1 mol of xylylenediamine), most of the reaction product is tarry material and the yield of xylyleneglycol is limited to only 10 to 20%.
As described above, when benzylamine derivative is diazotized and the resulting diazonium salt is decomposed, tarry substance is easily formed. This is supposed to be the reason why benzylalcohol derivative had not been produced industrially by diazotization of benzylamine-type compound.
The present inventors studied the method for producing xylyleneglycol by the reaction of xylylenediamine with nitrite in the presence of mineral acid and decomposition of the resulting diazonium compound and found that the formation of tarry substance has a close relation with the quantity of the water in the reaction mixture and the PH of the reaction mixture, the formation of the tarry substance is suppressed and xylyleneglycol is produced with high yield by controlling the quantity of water and PH, and have established the present invention.